Not Applicable
Plasma treatment of large area substrates such as glass or semiconductor substrates used in the fabrication of flat panel displays or 300 mm silicon wafers respectively pose a series of problems that do not occur in the processing of small area substrates. One problem is simply the generation of plasmas of sufficient area to treat the large area substrate. A second problem is the maintenance of the uniformity of the plasma density and chemistry over such a large area.
The use of inductively or transformer coupled plasma sources (ICP and TCP, respectively) are affected both by the difficulty of maintaining plasma uniformity using inductive coil antenna designs and the cost of fabricating and maintaining such systems which require large and thick quartz windows for coupling the antenna radiation into the processing chamber. The use of such thick quartz windows results in an increase in rf power (and reduction in efficiency) due to heat dissipation within the window.
The use of Electron Cyclotron Resonance (ECR) and Helicon type sources are limited by the difficulty in scaling the resonant magnetic field to large areas when a single antenna or waveguide is used. Furthermore, most ECR sources utilize microwave power which is more expensive and difficult to tune electrically. The use of hot cathode plasma sources results in the contamination of the plasma environment due to the evaporation of cathode material, while cold cathode sources result in contamination due to exposure of the cold cathode to the plasma generated.
The present invention avoids these problems encountered by previous large area plasma processing systems.
The present invention relates to an easily scalable and maintainable system for producing a uniform plasma of any size. In one embodiment a plurality of rf plasma sources are removably attached to the dielectric windows such as glass or quartz of a vacuum processing chamber, while in another embodiment each of the plurality of sources includes its own window and is attached to the chamber. Plasma measuring probes within the chamber provide information on the plasma uniformity and this information is used to control the rf energy applied to each of the rf plasma sources so as to maintain the desired uniformity. In one embodiment, the plasma measuring probes are Langmuir probes. In another embodiment, the probes are Faraday cups. In yet another embodiment, the probes are optical probes.
In another embodiment, a plasma source includes a quartz window with an integral tube for gas introduction. Several of such plasma sources using different gases may be combined in a linear array for the sequential treatment of substrates in an inline processing system.
In a further embodiment multiple antennae rf sources are used to provide a uniform plasma during the pulsing phase and steady state in order to provide a uniform ion implantation dose to a large area substrate. The plasma source is stationary and the wafers are transported through the plasma or the wafers are stationary and the plasma is transported past the wafers.